A photovoltaic cell (for example a solar cell) usually exhibits a layer of semiconductor material, for example silicon (also called photovoltaic layer in the text which follows). The photovoltaic layer exhibits a front (also called emitter side) and a rear, an (electrically conductive) contact pattern (for example in the form of so-called contact fingers) being applied to at least one of the two sides. The contact pattern typically has a width of at least 100 μm whilst its thickness is only about 10 μm to 15 μm. A greater width of the contact pattern leads to a reduction in the efficiency due to the resultant increased shading whilst a reduction in width results in the disadvantage that the line resistance of the contact pattern is increased. Furthermore, the current of the individual contact patterns is combined in so-called busbars as a result of which further shading of the front surface is caused.
Photovoltaic cells (for example solar cells) are generally interconnected by means of contact strips which are soldered to the busbars of the photovoltaic cell (for example solar cell). In this context, the entire current is conducted through the contact strips. To keep the resistance losses as low as possible, a certain total cross-sectional area of these contact strips is required. This results in a loss of power due to the shading on the front. A further disadvantage consists in that the busbar exerts mechanical stresses on the paste-wafer junction during soldering which can lead to a fracture of the photovoltaic cell.
To create an improved photovoltaic module, the contact pattern of the photovoltaic cell (for example solar cell) and the number and dimension of the contact strips (also called contact wires in the text which follows) should thus be optimized in combination.
In this context, it has been found that good optimization is obtained for many thin parallel contact wires. It can also be expected that due to the wires being fixed at selective points on the photovoltaic cell (for example solar cell) lower mechanical stresses are built up due to the different thermal coefficients of expansion of wire and photovoltaic cell (for example solar cell).
One problem in this is the handling and positioning of the thin contact wires on the photovoltaic cell (for example solar cell).
In patent specification DE 102 39 845 C1, a method is described in which the contact wires are fixed on an optically transparent film with the aid of an optically transparent adhesive and are subsequently fixed on the metallization of a solar cell. In this arrangement, film and adhesive remain in the solar cell module which implies relatively high demands on the adhesive and the film with regard to long-term stability and, as a result, causes relatively high costs. In this method, the wires are embedded in an optical transparent polymer carrier material and connected to the solar cell, the polymer auxiliary material being used for improving the manageability.